PHYSICS
Paper 3
PRACTICAL
Instructions to Candidates
- Answer ALL the questions in the spaces provided.
- Mathematical tables and electronic calculator may be used.
- Candidates should answer the questions in English.
Questions
QUESTION 1
You are provided with the following apparatus
- Two dry cells
- Nichrome wire mounted on the meter rule
- An ammeter
- Cell holder
- Voltmeter
- 8 connecting wires
- Switch
- A jockey
Proceed as follows.
- Determine the electromotive force of the dry cells.
E =…………………………………….. (1 mark) - Draw a diagram to show how the e.m.f,E of the dry cells is measured. ( 1 mark)
- Connect the circuit as shown below
Connect the ends of A and C where AC is 100 cm across the terminals as shown above. Close the switch and record both ammeter reading and the voltmeter reading.
Current I = …………………………… ( 1 mark)
P.d (V) =………………………………. ( 1 mark) - Proceed for the lengths shown in the table and record the corresponding values of current,I and voltage,V ( 6marks)
Length L(cm) 100 70 60 50 40 20 I(A) P.d(V) - Plot a graph of p.d,V(V) against current,I(A) (5 marks)
- Determine the slope of the graph. (3 marks)
- Given that E = V+Ir, determine the following using the graph above.
- Internal resistance r (1mk)
- The e.m.f E of the dry cells (1mk)
Question 2
PART A
You are provided with the following:
- A metre rule
- A knife edge
- One 50g mass and a 100 g mass
- Two pieces of threads each 30 cm long
- Some water in a beaker
- Liquid L in a beaker
- Tissue paper
Proceed as follows
- Balance the metre rule on the knife edge and record the reading at this point
Balance point =……………………………………cm mark (1 mark)
For the rest of this experiment the knife edge must be maintained at this position. - Set up the apparatus as shown in the figure below
The balance is obtained by adjusting the position of 100g mass when 50 g mass is fully immersed in water. Record the values of X and D.
X=…………………………………………………… ( 1 mark)
D=…………………………………………………… ( 1 mark) - Using the principle of moments;
- determine the weight W1of the 50g mass in water (2 marks)
- determine the Upthrust UW in water (1 mark)
- Remove the 50 g mass from the water and dry it using a tissue paper.
Keeping D constant, adjust the position of 100g mass until the metre rule is balanced and record the value of distance X.
X =…………………………………………………….. (1 mark)- Determine the weight W2 of the 50g mass in liquid L. ( 2 marks)
- Determine the Uphtrust UL in the liquid. ( 1 mark)
- Determine the relative density R.D of the liquid L, given that
R.D= UL (2marks)
UW - Find the density of liquid X in S.I unit (2marks)
PART B
You are provided with the following:
- A semi-circular glass block
- Soft board
- White paper
- Four Optical pins
- Two Thumb pins
- Vernier calipers
Procedure
- Measure the thickness of the glass block using the Vernier calipers provided
t = ________cm __________m (1mk) - Fix the plain paper to the soft board using drawing/thumb pins
- Place the semi-circular glass block on the paper and trace its outline. Remove the block and label A and B as shown in figure above.
- Identify the centre O of the plane and draw the normal at that point as shown in the figure above.
- Measure incident angle i as 480 then draw the incident ray
- Place two pins P1 and P2 on the incident ray as shown.
- Move your eyes at curved face and locate the images of pins P1 and P2, place pins P3 and P4 such that the four pins are aligned in a straight line.
- Remove the glass block and join points P3 and P4 to meet the interface AB.
- Measure the angle Y between incident ray and the reflected ray.
Y= ___________ (2 marks)- Find the value of M given that (3marks)
M = (tY/2)-1 - Hand in the white paper used (1mark)
- Find the value of M given that (3marks)
Confidential
Question 1:
- Two dry cells and a cell holder
- An ammeter
- A voltmeter
- Metre rule mounted with a nichrome wire( 28 gauge)
- A switch
- 8 connecting wires
Question 2
- Metre rule
- A knife edge
- 50g mass and a 100g mass
- Two pieces of threads each 30 cm long
- 100 ml of Water in a beaker
- 100 ml of glycerine(Liquid L) in a beaker
- Tissue paper
- 4 optical Pins
- semi-circular glass block
- two thumb pins
- soft board
- plain papers
- Vernier calipers
Marking Scheme
QUESTION 1
- E= 3.0V ± 0.1
-
- Current I = 0.12A ± 0.05
P.d(V) = 2.60V ± 0.10 -
Length L(cm) 100 70 60 50 40 20 I(A) 0.12 0.16 0.18 0.20 0.24 0.36 P.d(V) 2.60 2.45 2.40 2.20 2.10 1.75 -
- Slope = ΔV(v)
ΔI(A)
= 3.0 - 2.2
0 - 0.225
Slope = - 0.8
0.225
= -3.5556 Ohms -
- V= -Vi + E
y= mx + c
M= -r but
gradient = -3.5556
r = 3.5556Ω - e.m f , E= 3.0V
( accept students Y- intercept)
- Confirm from the graph
- V= -Vi + E
QUESTION 2
PART A
- Balance point = 50.0 ± 0.5 cm mark
- X= 17.5 ± 0.5cm
D= 39.8 ± 0.5cm -
- F1d1 = F2d2
W1 x 39.8/100 = 0.1 x 17.5/100
W1 = 0.0175
0.398
W1 = 0.04396N - Uw = WA - W1
=0.5 - 0.04396
= 0.456N
- F1d1 = F2d2
- X = 17.0 ± 0.5cm
- F1d1 = F2d2
W2 x 39.8/100 = 0.1 x 17.0/100
W2 = 0.04271N - UL = WA -WL = 0.5 0.04271
= 0.45729N
- F1d1 = F2d2
- R.D = 0.45729 = 1.002829
0.456
PART B
- T = 1.50CM 0.015M
- ...
- ...
- ...
- ...
- ...
- y= 96° ± 2°
- M = (0.015/2 x 96)-1 = 1.388
≈ 1.4 - Check the plain paper to confrim what the student has drawn
- M = (0.015/2 x 96)-1 = 1.388
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